In veiled chameleons (Chamaeleo calyptratus) it is very easy to see if you are dealing with a male or female. Since they are born the males will have spurs on its hind legs. These spurs are on the back of their feet, between the two parts of the toes and is facing backwards. These spurs are just a little bump but help the males stabilize when mating. The back and front feet of female chameleons all look the same and they have no spurs.
When veiled chameleons are older it can be even easier to see if you are dealing with a male or female chameleon. The males are larger, with a larger casque (crest on their head). Males often also show more strong coloration and more aggressive colors. The female is able to do the same color changes as the male, but is less easily inclined to.
Females sometimes show specific colors to indicate that she wants to mate or that she does not want to mate. If you see yellow spots and blue stripes on a dark skin on an adult Veiled Chameleon it is most likely a female (see picture).
Behavior differences in chameleon sexes
In behavior male and female veiled chameleons are pretty similar. Males can be a bit more aggressive than females. You don’t need to treat a female or male veiled chameleon differently, except that adult females always need a place to bury their eggs. Even if she has not been with a male, she can produce eggs. She needs some moist sand to dig into and lay her eggs. Usually you can see if she started to produce eggs, as she will get a big bumpy belly. If she cannot lay her eggs she could die.
Differences in sexes of other chameleon species
Not every species of chameleon has such an easy way to see which gender the chameleon has. In panther chameleons (Furcifer pardalis) you need to look at a slight bulge under the tail. Males have this bulge, females do not. In Jackson’s chameleon (Trioceros jacksonii) you can see the difference in sex clearly when the chameleons are adult, males have large horns and females do not.
With other species the chameleon sexes can not be distinguished without doing tests or observing their behavior.